how to drain an expansion tank that has no flow in valve?

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  #1  
Old 09-23-09, 02:01 PM
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how to drain an expansion tank that has no flow in valve?

Hi,

I have an old water boiler and a 15gal expansion tank. The boiler is Kenmore Boiler Sears Model (22996156). No manufacture info for the tank.

After some study on how expansion tank works, I started to think how to either check for water clogging or just drain this tank. I then noticed that there is only one hand valve for draining out of water, but no valve to control the flow between the boiler and the tank! And there is no way to look inside the tank -- a steel tank.

so does this means that if I want to drain this tank, i have to drain the whole system?

thanks!
 
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Old 09-23-09, 03:30 PM
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You say it's a '15 gallon' tank... so I assume that it means you have a standard steel 'compression' tank that's strapped into the joists above the boiler?

You may not have to drain the entire system, depending on what other valving is installed. In other words, if you can isolate sections of the piping, you may only have to drain a little bit.

Best bet to help us help you would be if you could take a bunch of pics, post them to a photo sharing site such as Image hosting, free photo sharing & video sharing at Photobucket ... it's a free service, set up an account and put the pics there. Leave a link here so we can view the album.
 
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Old 09-23-09, 04:24 PM
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You may not have to drain it. These were designed as maintenance free tanks. The problem is someone adds auto air vents cause the problems.
Run the boiler and built temperature in the boiler. Note the pressure at cold temp and when hot. Should not change too much. Normal is 2 - 5 psi. There may be some variations which may change the pressure more but never above 20 psi top pressure reading.
 
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Old 09-24-09, 10:35 AM
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Here are the pictures:

The first one is the whole view and the 2nd one is the inlet part of the tank.


And i am also showing the boiler display. After turn on the water, the pounds meter slowly increases and now it is reaching 45 pounds. I leave the valve on to see how far it will go. just want to know if this is normal?

by the way, i don't see anything related to pressure.

Pictures by lyrebird_bbs - Photobucket
 

Last edited by lyrebird; 09-24-09 at 10:58 AM.
  #5  
Old 09-24-09, 12:34 PM
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Originally Posted by lyrebird View Post
After turn on the water, the pounds meter slowly increases and now it is reaching 45 pounds. I leave the valve on to see how far it will go. just want to know if this is normal?
I would say it's not normal - and please don't try to find out how high it will go!

The pressure started rising after you opened the valve between the boiler and the city water supply? Without the boiler firing?

First of all, your relief valve should have lifted. It is typically set for 30psi. This is very troubling, and you can wind up overpressuring your boiler. (City water pressure at my house runs around 55psi.) Stop your experiment, close the valve, and bleed some water out of the boiler.

Your automatic fill valve may be leaking past its seat. If that's the problem, replace it - along with the relief valve if it didn't lift at 45 psi.

The red needle on your pressure gauge is for altitude - it is manually set, and it isn't set correctly. It should be set for about 25 ft for a 2-storey house with the boiler in the basement. That, then, marks your proper cold pressure.

P.S. I just read your questions that you attached as captions to your pictures. The first photo does not show a valve - it shows a pipe union and the equivalent to a Bell & Gossett airtrol tank fitting. In the third photo, showing the boiler pressure/temp gauge, you asked what "pounds" mean. It means pounds per square inch (psi).

I can tell you how to check for air in your expansion tank without draining the whole system. But but before we worry about that quite yet, you need to slow down and maybe get some help.
 

Last edited by Mike Speed 30; 09-24-09 at 12:58 PM.
  #6  
Old 09-24-09, 02:03 PM
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Thanks Mike, the relief valve turned on and the water was out. Then I saw your post. The boiler was not firing.

So let's put the expansion tank aside. I added one more picture for the Air purge (i think) in the link

Pictures by lyrebird_bbs - Photobucket

I hired a technician to teach me how to use the boiler. He told me to leave the main hand valve on, and the Red Bell-shaped stuff will automatic shut it off when the pressure reaches the limit.

So from today's experiment, is it safe to say the bell-shaped stuff is not working properly?


Originally Posted by Mike Speed 30 View Post
I would say it's not normal - and please don't try to find out how high it will go!

The pressure started rising after you opened the valve between the boiler and the city water supply? Without the boiler firing?

First of all, your relief valve should have lifted. It is typically set for 30psi. This is very troubling, and you can wind up overpressuring your boiler. (City water pressure at my house runs around 55psi.) Stop your experiment, close the valve, and bleed some water out of the boiler.

Your automatic fill valve may be leaking past its seat. If that's the problem, replace it - along with the relief valve if it didn't lift at 45 psi.

The red needle on your pressure gauge is for altitude - it is manually set, and it isn't set correctly. It should be set for about 25 ft for a 2-storey house with the boiler in the basement. That, then, marks your proper cold pressure.

P.S. I just read your questions that you attached as captions to your pictures. The first photo does not show a valve - it shows a pipe union and the equivalent to a Bell & Gossett airtrol tank fitting. In the third photo, showing the boiler pressure/temp gauge, you asked what "pounds" mean. It means pounds per square inch (psi).

I can tell you how to check for air in your expansion tank without draining the whole system. But but before we worry about that quite yet, you need to slow down and maybe get some help.
 
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Old 09-24-09, 02:20 PM
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Originally Posted by lyrebird View Post
I hired a technician to teach me how to use the boiler. He told me to leave the main hand valve on, and the Red Bell-shaped stuff will automatic shut it off when the pressure reaches the limit.

So from today's experiment, is it safe to say the bell-shaped stuff is not working properly?
That would be my conclusion.

The red thing in your newest photo is an automatic fill valve (not an air purge as you indicated in your caption). The bail on top is a manual fast-fill over-ride for filling the system. The automatic fill valve should admit water from the city system when the boiler pressure drops below the valve set-point, typically 12-15 psi. Has anybody been messing with the setpoint screw on top of the auto fill valve?

If your main valve connecting your system to the city water supply can shut off totally tight, you can operate the heating system with a leaky auto fill valve - and use the main valve, manually, as necessary for make-up to maintain system pressure. But in my opinion, the auto fill valve should be replaced.

You picture doesn't show it, but there should be a backflow preventer in the city-water feed line.

There should not be an air-eliminator device anywhere on your system - since it has a conventional expansion tank.
 
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Old 09-24-09, 03:11 PM
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lyrebird is an AMAZING bird! I know that this is off topic, but if anyone wants to be amazed at what the Lyrebird can do, Google and watch some video...

Lyrebird, I left pretty much the same comments that mike left here, over on your photobucket page.

I would like to see pictures of the entire system. Is there room to step back and take some wider shots of the system?

Hopefully the technician that you hired will be able to tell you what you need to know.
 
  #9  
Old 09-25-09, 08:58 AM
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Thanks guys. Now I more or less understand how the system works, after getting some damage. I guess this thing happens when you bought a 100-year old house and no technician can tell you exactly how the 50-year old unit works. Some technicians even told me this is a steam boiler since they cannot find a pump. Then I hired the one who used to maintain the boiler for the previous owner. He told me it uses the natural gravity and I SHOULD leave the water on and the automatic fill valve should shut off. And he said it looked quite new and I should not worry about that. He had left before the boiler reached 20 pounds (psi). And I DID NOT ask how many PSI is the proper value.

I wanted to change the boiler. But after yesterday's accident, I feel the boiler is not the most important one. I guess I need to replace the valve, and a bump to increase efficiency, and perhaps a backflow preventer?
 
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